1. Field of the Invention
The invention relates to a device for suspending posters, comprising a web of posters which can be driven back and forth between two rolls or rollers arranged spaced from each other one on top of the other. The web of posters is longitudinally tensioned in the direction of transport. There are holders that serve as lateral guides of the web that substantially reach from one roll to the other. These holders are associated with the reinforced longitudinal edges of the web of posters between the rolls.
The web of posters is generally moved back and forth vertically. However, the invention is not limited to the vertical direction of transport. The picture or poster displayed between the rolls may be inclined against the vertical or the movement of the picture may take place horizontally as well. Thus, even though only a vertical direction of transport is explained or claimed here and in the following, deviations from the vertical are included as well.
The device for suspending posters is suitable for displaying a poster in its total size. Preferably, two or more individual poster pictures can be assembled, for example by gluing, fusing or stapling them together, or with the help of some type of zipper, so that a web of posters is obtained. This web of posters is wound from one roll to the other in sections so as to permit recognition of the individual poster picture.
2. The Prior Art
If such a device for suspending posters is set up outdoors, the entire arrangement is usually surrounded by a showcase having a window made of glass or plastic on the viewing side. An advertising showcase of this type is described, for example in German Patent No. DE 29 51 0670 U1. If the viewing surface to be displayed exceeds a certain size, for example 3 by 4 meters, it is difficult to produce the transparent front glass pane and to transport it to the site of erection. For that reason, it has been proposed to assemble the front glass pane from a number of components. However, this is still expensive.
Poster materials are available which are weatherproof to such a degree that a front pane of the advertising showcase would not be needed even if such a showcase is set up outdoors. Generally, materials that are insensitive to moisture, such as plastic, textiles, coated paper or metal foil materials can be used for the web. Good results were obtained in practical applications with webs of vinyl. However, in practice, the front pane has nonetheless been required because the web of posters is exposed not only to sunlight and rain but also to wind or storm conditions. Even draft air in a hall may cause the web of posters clamped between the rolls to flutter if the front pane of the showcase is missing.
French patent application 99 12 424 describes a device for suspending posters of the type specified above. The device has an upper roll and a lower roll. A web of posters is wound back and forth between the rolls with the web in a longitudinally tensioned condition. In addition, the device comprises means for applying tension to the web of posters crosswise, the objective being that the web of posters will be capable of withstanding stress caused by wind gusts as well as other weather influences, and that it can be wound up uniformly without throwing folds.
As a means for applying the transverse tension, the French patent application proposes to equip the lateral longitudinal edges of the poster web with edge reinforcements, so-called welts, and to associate frame components each having a groove extending from roll to roll with the reinforced edges. The grooves extend across their entire length over the reinforced edges or welts similar to a pair of pliers. The grooves are designed so that the welts are supported in the grooves when the poster web is subjected to tensile stress in the transverse direction. xe2x80x9cWeltsxe2x80x9d are elastic edge reinforcements of a flat web, for example in the form of a cord made of leather or plastic, or in the form of coil springs made of metal.
According to the French patent application, the poster web must be kept taught with transverse tension along the reinforced longitudinal edges of the poster web running in the associated grooves, so that the poster web cannot flutter even in strong winds. When the poster web is wound further to change the poster picture, the reinforced edges must slide along in the hollow grooves. This means that substantial frictional forces occur when the poster web is moved on. In particular, static friction must be overcome when the poster web starts move, and requires substantial reinforcement of the driving means, which may easily cause the poster web to slightly tear or to be destroyed.
It is therefore an object of the invention to provide a poster changer in which the web of posters, which are tensioned in the longitudinal direction, can be displayed picture-by-picture, by moving the web of posters back and forth between two winding rolls, stabilized in both the longitudinal and transverse directions. The web thus has flat stabilization, even without a protective front pane, and does not have to overcome any notable forces of friction while the web is moving, or during the start of the movement.
The invention comprises a poster holding means comprising a poster web that is movable between two rolls and which is tensioned in the transport direction. The lateral longitudinal edges of the web are reinforced. There are holding means that consist of individual guide heads arranged with a spacing from each other on each of the surfaces of the poster web. Each guide head facing a surface of the poster web is exactly opposed by a guide head on the opposite surface of the poster web, so that a pair of guide heads is formed.
The mutual spacing of the guide heads of the individual pair, and the mutual spacing of two pairs of guide heads opposing each other with respect to the width of the poster web, must be selected so that the poster web is fixed without static transverse tension, i.e., tension between the longitudinal edges without any influence of external dynamic forces such as wind. Additionally, the web must be displaceable in the longitudinal direction with very little resistance. In other words, the longitudinal edges must be stabilized as if a person were holding the poster web with both hands spread out, but in an adequately loose manner, so that the web can loosely slide between two fingers of each hand or on each side when a force is acting on the web in the longitudinal direction.
The present invention allows the poster web to be rolled in the longitudinal direction from one roll to the other with almost the same ease as with a conventional poster changer, in which the edges of the poster web are free, i.e. not stabilized in any way. The surface of the poster web is nonetheless stabilized on the edges of the web so that the web can be subjected to the action of wind and weather without the risk of any annoying fluttering.
This is accomplished by the holding means associated with the edges of the poster web, which loosely stabilize the edges of the web in several sites in the longitudinal direction of the web. At the same time, the holding means permit the web to loosely slide through in the longitudinal direction of the web. According to the invention, the longitudinal edges of the web extending from the two rolls are guided both when a picture is standing still and when the web is moving from one poster picture to the next poster picture without any active (i.e. static) transverse tension originating from the holding means. The existence of the holding means alone allows the poster web to hold on tightly to the holding means in the presence of external dynamic forces acting on it, e.g. wind forces, similar to the way in which a person holds on to a staircase railing.
According to the invention, the tips of fingers are reproduced by the guide heads. The guide head may be rounded off at least at its side facing the associated surface of the poster web, preferably with a spherical shape. Furthermore, in a way similar to a finger tip, the free end of the guide head may be provided with a bolt extending approximately perpendicular to the surface of the poster. The bolt is rotatably supported, preferably turning about its longitudinal axis extending perpendicular to the surface of the poster.
The individual guide head may be realized in the form of a roller whose axis of rotation substantially extends parallel with the surface of the poster, and preferably transverse to the direction of transport. It is particularly preferred that the individual guide head is a spherical roll that is rotatably supported, turning about any desired axes. This can take the form of a self-supported ball rolling off on the surface of the poster.
The stabilization of the poster web edge between pairs of guide heads becomes particularly effective if the poster web has an edge reinforcement. An edge reinforcement in the form of a welt can be designed in many different ways. The web needs to be thicker along its reinforced edge than in the area bordering on the reinforced edge. The thickness of the poster web at the edge reinforcement should be adequately large in relation to the area bordering on it, to an extent such that the edge reinforcement is prevented from slipping through between the guide heads within the area of the holding means. Edge reinforcements with varying thicknesses and cross sectional shapes can be used, combined with approximately the same property of smooth running.
The guide heads or pairs of guide heads can be mounted on strips extending spaced from the surface of the poster web. The guide heads, rollers or balls can be secured on the strips so that they exactly oppose each other in pairs piece by piece with respect to the two surfaces of the poster web.
The mutual spacing of the guide within a pair generally should be smaller than the thickness of the respective edge reinforcement. In particular, the spacing of the guide heads of each pair should be larger than the thickness of the poster web bordering on the edge reinforcement. Preferably, the guide heads are in the form of spherical rollers. Such spherical rollers are generally known for removing adhesive and sliding friction, for example in ball roller tracks on which heavy objects are to be displaced. Each individual ball of such a track is normally received with easy rotation in a bearing surrounding more than half of its spherical surface, e.g. supported in a ball bearing.
The holding means have pairs of guide heads between which the individual rollers of the web can pass through almost without friction. The mutual spacing of adjacent pairs of guide heads measured in the direction from the top to the bottom winding roll is to be selected adequately large or smallxe2x80x94e.g. in the range of 5 to 20 cmxe2x80x94that the poster web can be laterally guided or retained and thereby stabilized across its surface even in the presence of strong winds, without any risk of throwing folds when it is further wound, or when a poster is standing still. In one embodiment, the mutual spacing of guide heads, for example spherical rollers neighboring each other one side of the web, amounted to about 10 to 15 cm. The mutual spacing of the pairs of guide heads is also dependent upon the size of the individual poster of the poster web, and on the stiffness of the material of the web.
The the individual guide heads within a pair are preferably spaced so that when a poster is changed, the web smoothly slides along the guide heads. If the poster web material is smooth (e.g. vinyl), and/or if the guide heads are rollers and preferably spherical rollers, practically no static friction occurs, and only minor negligible sliding friction.
In one embodiment, the holding means clamp the longitudinal edges in a force-locked manner between each other, preferably adjacent to any edge reinforcement, as well as when they roll off driven along the edges when being wound back and forth on the two surfaces of the poster web. The guide heads are rollers pressed against each other or against a sliding table, or belts pressed against each other or against a sliding table, and in particular, belts mounted across driven rollers. In such cases, smooth running of the web in its longitudinal direction is accomplished not through minimal friction of the guide heads but by driving the holding means.
According to another embodiment of the invention, at least one spreading means is provided as the guide head alone or as an additional means associated with the above-described holding means of each of the longitudinal edges. The spreading means consists of at least one driven helical spreader supported, for example as a shaft journal. The surface of such a helical spreader has beads diverging in the form of screw lines in the direction of the respective edge of the web. Such a spreader is rotated in such a direction and with such a speed (preferably deviating from the speed at which the poster web is transported) that the web is spread transversely to the direction of transport by the element touching the beads at the time. For example, the edge reinforcement can be eliminated in this case. The spreaders may cooperate in pairs, or for one pair of unwinding fingers rotating around their axes, in each case with a guide roll positioned between the fingers, as is known in the textile industry (See DE 25 58 162 C2). To eliminate damage to the poster web by the holding means, the spreading beads of the shaft journals or unwinding fingers, which may be cantilevered in the helical form, are in the form of brushes.